1. Field of the Invention
The present invention relates to an image forming apparatus that can perform preview processing on a print image of a page to be printed, a method for controlling the image forming apparatus, and a storage medium.
2. Description of the Related Art
A recent image forming apparatus, such as a digital multifunction peripheral (hereinafter referred to as “multifunction peripheral”), has a print canceling function for enabling a user to interrupt print processing arbitrarily if the user cannot accept a printed product during a printing operation. The print canceling function is useful to prevent the print processing from being performed unnecessarily. The resources required in printing can be saved effectively and a period of time during which the multifunction peripheral is occupied by a single job can be reduced.
However, in many cases, the time when a user can determine acceptability of a printed product is later than the time the printed product is output actually. As a result, a significant amount of printed products will be output uselessly.
To solve the above-described problem, as discussed in Japanese Patent Application Laid-Open No. 2004-351872, it is conventionally feasible to discriminate a print completed portion of a print image from an unprinted portion on the image during a printing operation.
In general, the print processing to be performed by a multifunction peripheral includes a plurality of stages, such as paper feeding, transfer, fixing, and discharge. When a document to be printed includes a plurality of pages, the multifunction peripheral performs pipeline processing for simultaneously printing a plurality of pages instead of performing the processing thoroughly for each page.
For example, in a state where two pages are on the discharge stage and the transfer stage, respectively, a user may find an unnecessary print when the user is checking a preceding page. In this case, even if the printing operation is canceled immediately, a succeeding page (i.e., the page on the transfer stage) will be fixed and discharged sooner or later.
In this case, not only the preceding page (i.e., the cause of the print cancellation) but also the succeeding page (i.e., the page whose print processing was not stopped) are uselessly output as printed products. Further, according to the above-described conventional technique, the displayed images include all of the unprinted portions. In other words, the portions whose print processing is unstoppable are displayed unnecessarily.